George Zimmerman’s father, Robert Zimmerman Sr., testifies for the defense during his sons trial in Seminole circuit court in Sanford, Fla., on Wednesday.

SANFORD, Fla. — After taking less than a week to call 18 witnesses, George Zimmerman’s defense attorneys rested their case Wednesday in the neighborhood watch volunteer’s second-degree murder trial.

Prosecutors called their first rebuttal witness immediately afterward— Adam Pollock, the gym owner who had trained Zimmerman. Following rebuttal witnesses, prosecutors and defense attorneys will then work out the jury instructions before presenting closing arguments. The judge then sends the case to six jurors.

Zimmerman never testified. But jurors saw repeated video recordings of Zimmerman telling his side of the story to police investigators. The defense started its case last Friday, and it presented half as many witnesses in half the time that prosecutors did.

The defense rested on a day when the judge made two rulings that prevented them from introducing two pieces of evidence. Defense attorneys had wanted to present to jurors text messages discussing fighting from Trayvon Martin’s cell phone and an animation depicting Zimmerman’s fatal fight with Martin. But Judge Debra Nelson sided with prosecutors, who had argued the animation is inaccurate and the texts were irrelevant.

During the four days they presented their case, defense attorneys called Zimmerman’s friends, parents and uncle to testify that it is Zimmerman screaming for help on a 911 call that captured sounds of the fatal fight. Martin’s mother and brother had testified for the prosecution that it was Martin yelling for help.

Convincing the jury of who was screaming for help on the 911 tape has become the primary goal of prosecutors and defense attorneys because it would help jurors evaluate Zimmerman’s self-defense claim.

Zimmerman’s father, Robert Zimmerman Sr., was the last witness called by the defense on Wednesday, and he said it’s his son yelling for help on the call.

Defense attorneys also called a forensic pathologist who testified that the forensics evidence supports Zimmerman’s account of what happened.

Zimmerman has pleaded not guilty to second-degree murder and says he shot an unarmed Martin in self-defense during a scuffle in the townhome complex where he lived in February 2012. Martin was there visiting his father and his father’s fiancee. Some civil rights activists argued that the initial delay in charging Zimmerman was influenced by Martin’s race. Martin was black and Zimmerman identifies himself as Hispanic. The 44-day delay in Zimmerman’s arrest led to protests around the nation.

Earlier Wednesday, defense attorneys called public safety consultant Dennis Root to testify that Martin was in better physical shape than Zimmerman, and that the neighborhood watch volunteer wasn’t any athlete.

“He would find himself lacking when compared to Mr. Martin,” Root said of Zimmerman.

During cross-examination of Root, prosecutor John Guy used a life-sized foam mannequin in front of the jury to simulate the body positions of Zimmerman and Martin at the time of the shooting.

Straddling the dummy, Guy proposed a scenario in which Martin was on top of Zimmerman and asked Root if it was possible that Martin was backing away from Zimmerman at the time of the fatal gunshot.

“Yes,” Root said.

Root also said he may have taken different actions if he were in Zimmerman’s situation, but said that “it’s just a matter of what you as the individual view as options.”

Using the same mannequin during further questioning of Root, defense attorney Mark O’Mara challenged the notion of Martin retreating. Root said that while multiple gun angles were possible, he had no specific information to say what position Martin was in when he was shot.

“I think you’re not going to be involved in a conflict like this without it being dynamic,” Root said.